The contribution of splanchnic and extrasplanchnic tissues to the blood metabolic clearance rate (MCR) of progesterone will continue to be studied. The uterine extraction of progesterone will be studied in non- pregnant women and the conversion of progesterone to 20 alpha- hydroxypregn-4-en-3-one (20 alpha-OHP) and 5 alpha-pregnan-3,20-dione (5 alpha-DHP) estimated. The splanchnic extraction of progesterone in non- pregnant and pregnant subjects will be determined by the indirect method (simultaneous administration of radioactive labeled progesterone orally (C14) and intravenously (H3)). The MCR of progesterone will also be studied in anephric patients and in patients with minimal renal function. The brain extraction of progesterone, the distribution of progesterone in the brain, and metabolism of progesterone to 20 alpha- OHP and 5 alpha-DHP will be studied by the continuous infusion of (H3) progesterone to adult female monkeys. The effect of estrogen on the MCR and metabolism of progesterone in ovariectomized, hysterectomized women will be correlated with the effect of estrogen on the MCR of cortisol, the plasma concentration of cortisol and the plasma concentration of transcortin. To study the biological activity of progesterone and the uterus, the "uteroglobin" concentration of rabbit uterine fluid will be assayed. The interrelationship of estradiol and progesterone on uteroglobin secretion will be studied and also the relationship between uterine extraction and metabolism of progesterone to the secretion of uteroglobin.